<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let score=Number(prompt(''))
        if (score>=90){
            alert('A')
        }else if (score>=80 && score<90){
            alert('B')

        }else if (score>=70 && score<80){
            alert('C')

        }else if (score>=60 && score<70){
            alert('D')

        }else if (score<60){
            alert('E')

        }
    </script>
</body>
</html>